Recorder Output - Varian sentorr Instruction Manual

3-5

RECORDER OUTPUT

Recorder output for each gauge is provided at the back of the unit. A two-conductor Micro Jax con-
nector is plugged into each output. Varian strongly recommends the use of shielded wiring (coaxial
cable) to maintain compliance with FCC regulations for radiated emissions. Refer to Figure 3-3 to
assemble the cable. Any recorder with an imput impedance greater than 2,000 ohms and a full-scale
input range of +10 V can be used.
The output reflects the displayed pressure of the gauges. Refer to Figures 3-4a and 3-4b for standard
and linear output characteristics of the recorders.
Ion Gauge Algorithm: Converting recorder output voltage to pressure
To calculate the pressure from the voltage output
To get the exponent, take the integer part of voltage output which is 4 and subtract 11:
To find the mantissa, take the fractional portion and add .1 to it and divide by .11
therefore:
TC ConvecTorr Algorithm: Converting recorder output voltage to pressure
To calculate the pressure from the voltage output
To get the exponent, take the integer part of voltage output which is 3 and subtract 4:
Now to find the mantissa, take the fractional portion and add .1 to it and divide by .11:
therefore:
Operation
Figure 3-3. Assembling the Cable
Example recorder output = 4.28 volts DC
4 – 11 = –7 (E-7)
(.28 + .1)/.11 = 3.45
4.28 VDC = 3.45E-7 Torr
Example recorder output = 3.28 volts DC
3 – 4 = –1 (E-1)
(.28 + .1)/.11 = 3.45
3.28 VDC = 3.45E-1 Torr
3-6